The present invention relates to a camshaft phaser for controlling the phase relationship between the crankshaft and a camshaft of an internal combustion engine; more particularly, to a vane-type phaser having a locking mechanism for selectively locking the rotor to the stator; and most particularly, to a locking mechanism for a vane-type phaser wherein a locking pin extends beyond the rotor chamber such that the pin may be manually withdrawn from locking engagement by an operator during mounting of the phaser to an engine to avoid torque damage to the locking pin mechanism.
Camshaft phasers for internal combustion engines are well known. Typically, a camshaft phaser is disposed on the front of an engine and includes an oil control valve for controlling oil flow into and out of the phaser. The valve receives pressurized oil from an oil gallery in the engine block and selectively distributes oil to timing advance and retard chambers within the phaser to controllably vary the phase relationship between the engine""s camshaft and crankshaft. In a vane-type phaser, the chambers are formed between inwardly-extending lobes of a generally cylindrical stator and outwardly-extending vanes of a rotor concentrically disposed within the stator.
At various times during the operation of an engine and its associated phaser, it is desirable to rotationally lock the rotor to the stator. For this purpose, a prior art phaser may include a locking pin mechanism in a rotor vane. The mechanism typically includes a sleeve disposed in a bore in the vane and a spring-biased locking pin disposed in a well in the sleeve. The pin is biased to lock into a corresponding well in the sprocket to which the stator is mounted whenever the pin and sprocket well are rotationally aligned. The sprocket well communicates hydraulically with an oil pressure source to automatically force the pin from the sprocket well when certain engine operating conditions are met.
A problem can arise during mounting or removal of the assembled phaser to an engine camshaft. The locking bolt bears on the rotor and hence can exert torque on the rotor as the bolt is being tightened. If the pin is engaged at that time, the pin may be damaged by torque from the rotor. In the prior art, it is generally not possible to ensure that the pin is not engaged as the bolt is tightened.
Another problem encountered in the prior art is the inability to easily confirm the position of the locking pin relative to the sprocket well when the engine is operating.
What is needed is a means for assuredly unlocking the locking pin from the sprocket well during mounting or removal of a phaser to an engine to prevent torque damage to the locking pin mechanism.
What is also needed is a means for detecting the position of the locking pin while the engine is operating.
It is a principal object of the present invention to prevent damage to a locking pin mechanism during mounting or removal of a camshaft phaser to an engine.
It is a further object of the present invention to provide a means for determining the position of the locking pin during engine operation.
Briefly described, a locking pin mechanism in accordance with the invention is disposed in a bore in rotor vane for controllably engaging a well in the camshaft sprocket to rotationally lock the rotor and stator together. The mechanism comprises a lock pin sleeve disposed in the bore and extending from the vane through an arcuate slot in the inner cover plate. The sleeve terminates in an enlarged head outside the inner cover plate. Preferably, the slot includes a portion wide enough to permit passage of the head through the slot during assembly of the phaser. The slot extends through a central arc at least equal to the actuation arc of the rotor within the stator, preferably about 30xc2x0. Disposed within the sleeve is a slidable lock pin having a locking head for engaging the sprocket well and a tail portion extending through the sleeve head. A compression spring within the sleeve urges the pin into lock relationship with the sprocket well whenever they are rotationally aligned. A groove in the sprocket connects the well with an oil source in the assembled phaser such that oil pressure overcomes the spring to retract the pin, unlocking the rotor from the stator.
The tail portion of the lock pin extends beyond the cover plate and the sleeve head, permitting the lock pin to be manually retracted by an operator while the phaser is being installed or removed from the engine, thus preventing damage from high torque exerted via the phaser attachment bolt in bolting the phaser to or removal from the engine. A sensing device, such as a Hall Effect sensor, placed proximate the tail portion of the locking pin, can be used to detect the position of the tail portion, and therefore the relative position of the locking head and the sprocket well while the engine is running.